The invention relates to a cartridge system which is especially matched to the properties of plastic-clad monolithic chromatography columns.
Columns for chromatography, in particular for HPLC, usually have a cladding of metal or plastic into which the sorbent has been introduced. Besides conventional particulate sorbents, monolithic sorbents, as disclosed, for example, in WO 94/19687 and in WO 95/03256, are also gaining increased importance.
In order to produce columns with particulate sorbents, column tubes, typically of metal or plastic, are sealed at one end with a filter system and filled with the sorbent under pressure. During this operation, it is ensured that the sorbent particles fill the entire tube in order that no dead space is formed which could impair the separation efficiency. After filling, the column is sealed at both ends with integrated or attached filter systems in order that sorbent cannot escape during use. The connection to eluent feed and discharge takes place through screw connections, which are screwed directly onto the column (for plastic or metal columns) or via re-usable cartridge systems which are inserted into the columns (for metal columns).
In contrast to particulate sorbents, which can be introduced into prefabricated metal columns, some peculiarities have to be taken into account in the cladding and connection of monolithic sorbents: Monolithic sorbents are generally removed from the mould after production and re-clad for use. Since monolithic sorbents have a rigid shape and dead spaces arising during the cladding cannot be compensated for, the cladding of the monoliths must be carried out with no dead space and in a pressure-stable manner. It has been found that plastic cladding is particularly suitable since it has adequate pressure stability and can be applied to the monolithic sorbent with no dead space. The sorbent generally terminates flush with the cladding at the ends.
Monolithic columns have hitherto been connected to the eluent feed or outlet via screw connections, which are screwed directly onto a thread cut into the plastic cladding. If the screw connection is removed, the monolithic sorbent is directly accessible and can easily be damaged. A connecting system for monolithic plastic-clad sorbents in the form of a cartridge system was hitherto unknown. Owing to the material properties of sorbent and cladding, the metal cartridge systems known for particulate sorbents cannot be applied to monolithic plastic-clad sorbents. In particular, different demands are made of column termination elements, such as, for example, filter elements.
The object of the present invention was therefore to develop a connecting system for plastic-clad monolithic sorbents which enables use as a cartridge system.
It has been found that a cartridge system consisting of a column with cap which is installed directly on the ends of the cladding, a spacer ring for integration of a pre-column, a divided supporting screw and an end piece which can be screwed onto the supporting screw for the connection of eluent feed and discharge meets all requirements of a connecting system for columns comprising plastic-clad monolithic sorbents.
The present invention therefore relates to a cartridge system at least comprising
a cartridge consisting of a plastic-clad column with monolithic sorbent on which a cap is installed at least at one end,
and a plastic connecting system consisting of at least one divided supporting screw and at least one end piece which is screwed onto the said supporting screw for the connection of eluent feed and discharge.
In a preferred embodiment, a device is present which enables the supporting screw to be placed against the cartridge at at least two different defined points. This device can be, for example, at least one spacer ring or a shape (for example recess or bead) provided for this purpose in the cap.
In a particularly preferred embodiment, the device is at least one spacer ring.
In a preferred embodiment, the cartridge cap has an internal thread for screwing onto the column.
The present invention also relates to the use of the cartridge system according to the invention for the chromatographic separation of at least two substances.